Lipid regulation of placental mycotoxin transport

During pregnancy, the placental BCRP/ABCG2 efflux transporter prevents the transplacental transfer of chemicals and protects the fetus from exposure to toxicants. Prior studies have demonstrated that BCRP can transport zearalenone, an estrogenic mycotoxin produced by fungi that grows on cereal crops. However, there is little known regarding the neonatal outcomes of compromised placental BCRP function in pregnant women exposed to zearalenone. Because of its estrogenic activity, in utero exposure to zearalenone could potentially increase the risk of altered sexual development and certain cancers. The purpose of this dissertation was to determine the influence of lipids on the expression and function of placental BCRP and its impact on the placental distribution of zearalenone during pregnancy. In both in vitro transwell models of the placental barrier (Marine Darby Canine Kidney cells and BeWo trophoblasts) and in vivo experiments with C57BL/6 mice, BCRP/Bcrp prevented the maternal-to-fetal transfer of zearalenone. Anandamide, an endocannabinoid, is known to influence placental development and function and may play a role in certain diseases of pregnancy. Studies using both human term placental explants and BeWo trophoblasts revealed that anandamide can down-regulate BCRP mRNA transcription and protein expression via a CB2-cyclic AMP signaling pathway. In BeWo trophoblast cells, anandamide increased the retention of Hoechst 33342, a fluorescent BCRP substrate, and zearalenone without directly inhibiting BCRP. Anandamide also decreased the basolateral-to-apical transport of glyburide, a BCRP substrate prescribed for gestational diabetes. Detailed analysis of human placenta specimens and BeWo trophoblasts also revealed that BCRP function is dependent on membrane cholesterol. Specifically, lipid raft isolation by density gradient ultracentrifugation demonstrated that BCRP is localized to lipid rafts in both BeWo trophoblasts and human placentas. Pre-treatment with cholesterol lowering agents pravastatin and methyl-β-cyclodextrin decreased BCRP efflux of both Hoechst 33342 and zearalenone without altering BCRP surface expression. Taken together, these data provide evidence that BCRP is important in protecting the fetus from exposure to zearalenone and that this function can be influenced by certain classes of lipids.Ph.D.Includes bibliographical referencesby John Thomas Szilagy